Microwave crystal detector with selfcontained co-axial mounts of diameter smaller than that of diode shell



March 1, 1966 AXI MOUNTS DI TER SMALLE T N THAT DIO SHELL Filed July 30, 1965 v. s. ROSE 3,238,427 MICRO E CRYSTAL DETECTOR WITH SELF-CON INED AGE/V7 United States Patent 6 (Granted under Title 35, US. Code (1952), see. 266) The invention described herein may be manufactured and used by or for the Government of the United States ofAmerica for governmental purposes without the payment of any royalties thereon or therefor.

This invention relates to broad-band microwave crystal detectors and more particularly to a sub-miniature broadband microwave crystal detector having a self-contained coaxial mount.

Although tripolar crystal diodes of the type employed in the present invention have been in existence for several years the mounts utilized to connect these crystals into video receiving systems have been generally bulky and not without significant weight thus depreciating the substantial savings in size and weight contributed to microwave systems by the crystal detector itself. Elimination of size and weight in crystal video receiving systems is a vital factor in many applications thereof such as in missile and space satellite systems requiring extremely small and light components; in portable or personal microwave surveillance receivers, subminiatu-rized for concealed use; in direction finding equipment requiring many crystals and crystal mounts in each equipment item; and in aircraft or shipboard equipment in which the location of the RF. components is such as to limit the space available therefor.

The self-contained or associated mounts of the present invention provide a broadband microwave crystal detector wherein the greatest portion of the unit size and weight is contributed by the tripolar crystal cartridge itself with a minimal contribution to such size and weight by the connector or mount portions. The over-all length of the crystal cartridge and mount is only slightly longer than a conventional crystal cartridge permitting in line application of the rectifier without substantial lengthening of the circuit and without any significant loss in sensitivity as compared with the sensitivity of crystals employing the heavier, larger type N and type BNC connectors.

The novel crystal diode detector assembly of the present invention includes a threaded connector extension of the outer conductive shell at both the RF. input end and the video output end and a pair of spring finger connectors one associated with the center conductor at the RP. input end and One associated with the crystal mounting block at the video output end of the rectifier. The novel connector configuration permits ready insertion of the tripolar crystal detector into a standard microwave system and is particularly adapted to accommodate the commercial Microdot connector.

It is an object of the present invention to provide light weight microwave crystal connectors or mounts.

Another object of this invention is to provide a microwave crystal with associated connectors wherein the crystal detector constitutes a substantial portion of the size and weight of the combination.

A further object of this invention is the provision of a microwave crystal detector and connector or mount package wherein the connectors or mounts constitute only a minor percentage of the over-all weight and size of the package.

A still further object of the present invention is the provision of a microwave crystal detector unti having self-contained connectors in which the over-all configuration of the unit is substantially linear.

These and other objects and many of the attendant advantages of the present invention will become more readily appreciated when the following detailed description is considered in connection with the accompanying drawing in which:

FIG. 1 is a sectional view of the crystal detector and associated connector of one embodiment of the present invention; and

FIG. 2 is a sectional view of another embodiment of the crystal detector and associated connectors of the present invention.

Referring now in detail to the drawings, wherein like reference characters represent like parts, there is shown in FIG. 1 an embodiment of the present invention employing a standard commercial coaxial type silicon tripolar crystal diode generally designated 10. The commercial crystal detector 10 conventionally includes a tubular brass outer conductive sheel 12 having a ceramic insulating bead 14 secured therewithin approximately midway along the length thereof for locating and support ing a brass center conductor 16. Also mounted Within outer sheel 12 adjacent the video output end thereof is a brass mounting block 18 spaced from outer shell 12 by a Teflon insulating sleeve 20. The Teflon insulating sleeve 20 provides a capacitance between the outer conductive shell 12 and the video signal center conductors thereby establishing the RF. by-pass capacity. Conventionally a capacitance of about 7 nnf. is employed but this may be varied as desired by merely changing the length of the block and insulator 2t). Mounted on mounting block 18 is the conventional silicon water or crystal 22 in point contact with whisker 24 attached to the coaxial center conductor 16.

In accordance with the present invention the above described tripolar crystal diode is adapted for in-line conneotion into a microwave system by means of a pair of mounting or connector plugs 26 and 36. Mount or connector plug 26, preferably of a silver plated brass construction, is secured to the outer conductive shell 12 at the RF. input end of the tripolar crystal by a press fit and conductive cement or any other suitable means and includes a threaded extension 28 and central passage 30. A coin silver, spring fingered, connecting clip 32 having resilient finger like construction at each end thereof is secured by a press fit within central passage 30 and spaced from plug 26 by an insulating bushing 34 of Teflon or similar material. The spring fingered connector clip 32 is adapted to resiliently grip center conductor 16 with its inwardly directed fingers while the outwardly directed fingers are adapted, in conjunction with threaded extension 28, to connect to a standard Microdot coaxial connector.

At the video output end of the crystal diode a mount or connector plug 36 is also secured to outer conductive shell 12 by means of a press fit and conductivecement in a manner similar to the mounting of input end plug 26. Output end plug 36 includes threaded extension 38, central passage 40, spring fingered connecting clip 42 and insulating bushing 44 secured in the same relationships and of the same materials as their counterparts 28-34 in input end plug 26. The inwardly extending spring fingers of connecting clip 42 are resiliently engaged with the lateral surfaces of a bored connecting seat or opening 46 in the base of brass mounting block 18 while the outwardly directed fingers are adapted, in conjunction with threaded extension 38, to connect the video output end of the crystal and mount package to a standard Microdot coaxial connector.

It will be apparent from the foregoing that the embodiment of FIG. 1 provides a compact crystal and mount package employing a standard tripolar crystal diode as the basic element and in which a substantial portion of the overall crystal and mount size and weight is attributable solely to the crystal diode itself.

Another embodiment of the present invention is shown in FIG. 2. In the FIG. 2 embodiment the crystal detector having self-contained mounts includes a two part tubular outer conductive shell 112, preferably of brass, having a reduced, threaded end portion 115 at the RF. input end thereof and an integral reduced threaded end portion 113 at its video output end. Though the shell configuration shown in FIG. 2 is not commercially available, it is fabricated so that the reduced threaded extension is integral with shell 112 in accordance with well-known manufacturing methods. The two part construction of outer shell 112 facilitates fabrication of the crystal diode and the two parts are preferably secured together at 111 by a conductive cement. It should be understood that any of a number of methods may be employed to secure the two parts of the outer conductive shell together consistent with accepted fabricating procedures. The only specific requirement being that good surface conductivity be maintained across the junction.

Mounted within outer conductive shell 112 is a ceramic bead 114 for locating and supporting a brass center conductor 116 having spring finger connectors 117 at the RF. input end thereof and whisker 124 attached to the other end thereof. A brass mounting block 118 is also mounted within outer conductive Shell 112 between the video output end and the ceramic insulating bead. The mounting block is spaced from outer conductive shell 112 by a Teflon insulating sleeve 120 which serves as a capacitance in the same manner as insulating sleeve 20 of the FIG. 1 embodiment.

Mounting block 118 has a silicon crystal 122 mounted on the RI. input side thereof which is in point contact with whisker 124 mounted on coaxial center conductor 116. On the opposite or video output side of mounting block 118 and integral with conductive shell 112 is a coaxial extension which includes a spring finger connector 119 at its outer end. An insulating bushing 134 provides for the spaced securing of spring connector 117 coaxially within threaded end portion 115 and insulating bushing 144 performs the same function between spring connector 119 and threaded end portion 113. The described relationship of spring connector 117 to threaded end portion 115 and spring connector 119 to threaded end portion 113 provides for the ready connection of both the RF. input and video output ends of the tripolar crystal diode package to standard Microdot coaxial connectors.

Each of the foregoing embodiments of the present invention provides an extremely small light weight coaxial crystal detector package for subminiature microwave application in which a substantial portion of the overall size and weight of the package is attributable to the crystal detector elements alone rather than to the mounts as found to be generally the case in presently available microwave crystal detector devices.

Obviously many modifications and variations of the present invention are possible in light of the foregoing teachings. It is therefore to be understood that the scope of the present invention is to be limited only by the appended claims and not otherwise.

What is claimed is:

1. A microwave crystal detector with self-contained coaxial mounts comprising:

(a) a tubular outer conductive shell having a threaded connector extension of reduced diameter at each end thereof,

(b) a center conductor mounted within and coaxial with said shell adjacent one end thereof,

(c) a mounting block mounted within said shell adjacent the other end thereof,

(d) said mounting block being spaced from said outer shell by an insulating sleeve,

(e) a crystal mounted on said block,

(f) a whisker in point contact with said crystal mounted on said center conductor,

(g) a first spring fingered clip on said center conductor extending within and insulated from one of said threaded connectors, and

(h) a second spring fingered clip coupled to said block extending within and insulated from the other of said threaded connectors whereby the crystal detector may be quickly and easily connected into a microwave system.

2. In a microwave crystal detector including an outer conductive shell, spaced coaxial center conductor, point contact crystal and whisker combination and a built in RF. by-pass capacity on the crystal mounting block the improvement comprising:

(a) a first threaded connector extension of reduced diameter on the R.F. input end of said outer conductive shell,

(b) a first spring clip on said center conductor extending coaxially within and insulated from said first threaded connector extension,

(c) a second threaded connector extension of reduced diameter on the video output end of said outer conductive shell, and

(d) a second spring clip coupled to said crystal mounting block extending coaxially within and insulated from said second threaded connector extension whereby said crystal detector may be quickly and easily connected into a microwave system and wherein a substantial portion of the size and Weight of the combination is provided by the crystal detector alone.

3. In a microwave crystal detector including an outer conductive shell, spaced coaxial center conductor, point contact crystal and whisker combination and built in RF. by-pass capacity on the crystal mounting block the improvement comprising:

(a) a first end plug including a first threaded connector extension of reduced diameter secured to the RF. input end of said outer conductive shell,

(b) a first spring clip on said center conductor extending coaxially within and insulated from said first end plug,

(c) a second end plug including a second threaded connector extension of reduced diameter on the video output end of said outer conductive shell, and

(cl) a second spring clip coupled to said crystal mounting block extending coaxially within and insulated from said second end plug whereby said crystal detector may be quickly and easily connected into a microwave system and wherein a substantial portion of the size and weight of the combination is provided by the crystal detector alone.

4. A microwave crystal detector including self-contained coaxial connectors and having an RF. input and a video output comprising:

(a) a tubular outer conductive shell,

(b) a center conductor,

(c) a ceramic bead secured within said outer conductive shell for mounting and maintaining said center conductor coaxial with said outer shell, the outer end of said center conductor terminating adjacent the RF. input end of said outer shell and the inner end of said center conductor terminating substantially mid-way along the longitudinal axis of said outer shell,

(d) a crystal mounting block mounted within said outer shell between the inner end of said center conductor and the video output end of said outer shell, said crystal mounting block being spaced from said outer shell by an insulating sleeve and having a connector receiving recess facing in the video output direction,

(e) a crystal Wafer mounted on the side of said mounting block opposite said recess,

(f) a whisker mounted on said inner end of said center conductor and positioned for point contact with said crystal wafer,

(g) a first end plug having a threaded connector extension of reduced diameter and a central bore therethrough secured to the RF. input end of said outer conductive shell,

(h) a first spring finger connector mounted within said bore in said first end plug and spaced therefrom by a first insulating bushing, one end of said spring finger connector resiliently engaging the outer end of said center conductor,

(i) a second end plug having a threaded connector extension of reduced diameter and a central bore therethrough secured to the video output end of said outer conductive shell, and

(j) a second spring finger connector mounted within said bore in said second plug and spaced therefrom by a second insulating bushing, one end of said spring finger connector resiliently engaging the recess in said mounting block.

5. A microwave crystal detector including self-contained coaxial connectors and having an RF. input and a video output comprising:

(a) a tubular outer conductive shell having a reduced diameter externally threaded end portion at both the RF. input and video output ends thereof,

(b) a center conductor having a spring fingered clip at one end thereof and a whisker mounted on the other end thereof,

(c) a ceramic bead secured within said outer conductive shell for mounting and maintaining said center conductor coaxial with said outer shell, the spring fingered clip end of said center conductor being disposed within and insulated from said threaded end portion at the RF. input end of said outer shell,

((1) a crystal mounting block mounted within said outer shell between the whisker carrying end of said center conductor and the video output end of said outer shell, said crystal mounting block being spaced from said outer shell by an insulating sleeve and having an extension thereon terminating in a spring fingered clip, said spring fingered clip on said extension being disposed within and insulated from said threaded end portion at the video output end of said outer shell, and

(e) a crystal Wafer in point contact with said whisker mounted on the side of said mounting block opposite said extension.

References Cited by the Examiner UNITED STATES PATENTS 2,438,521 3/1948 Sharpless 317236 2,777,995 1/ 1957 Henning 324-95 2,840,710 6/1958 Levy 329205 HERMAN KARL SAALBACH, Primary Examiner.

ALFRED BRODY, Examiner.

P. GENSLER, Assistant Examiner. 

2. IN A MICROWAVE CRYSTAL DETECTOR INCLUDING AN OUTER CONDUCTIVE SHELL, SPACED COAXIAL CENTER CONDUCTOR, POINT CONTACT CRYSTAL AND WHISKER COMBINATION AND A BUILT IN R.F. BY-PASS CAPACITY ON THE CRYSTAL MOUNTING BLOCK THE IMPROVEMENT COMPRISING: (A) A FIRST THREADED CONNECTOR EXTENSION OF REDUCED DIAMETER ON THE R.F. INPUT END OF SAID OUTER CONDUCTIVE SHELL, (B) A FIRST SPRING CLIP ON SAID CENTER CONDUCTOR EXTENDING COAXIALLY WITHIN AND INSULATED FROM SAID FIRST THREADED CONNECTOR EXTENSION, (C) A SECOND THREADED CONNECTOR EXTENSION OF REDUCED DIAMETER ON THE VIDEO OUTPUT END OF SAID OUTER CONDUCTIVE SHELL, AND (D) A SECOND SPRING CLIP COUPLED TO SAID CRYSTAL MOUNTING BLOCK EXTENDING COAXIALLY WITH SAID INSULATED FROM SAID SECOND THREADED CONNECTOR EXTENSION WHEREBY SAID CRYSTAL DETECTOR MAY BE QUICKLY AND EASILY CONNECTED INTO A MICROWAVE SYSTEM AND WHEREIN A SUBSTANTIAL PORTION OF THE SIZE AND WEIGHT OF THE COMBINATION IS PROVIDED BY THE CRYSTAL DETECTOR ALONE. 